1. Field of the Invention
The present invention relates to a method and apparatus for producing hydrogen peroxide by injecting minute bubbles of hydrogen and oxygen into a liquid stream of a carbon containing liquid phase reaction medium and a supported metal catalyst in which the liquid stream flows at high velocity.
2. Description of the Related Art
It is known that a mixture of gaseous oxygen and gaseous hydrogen forms an explosive mixture. Virtually all currently produced hydrogen peroxide is produced by indirectly combining hydrogen and oxygen. Thus, the primary conventional industrial method for production of hydrogen peroxide uses a chemical agent such as an alkylanthraquinone—ethyl or tertiary butyl anthraquinone. The anthraquinone is first hydrogenated to a hydroquinone and then oxidized with air to produce hydrogen peroxide and the original alkylanthraquinone. The anthraquinone specie is recycled back to the process. To solubilize the anthraquinone and hydroquinone, large volumes of a corresponding carbinol, methylnaphthalene and other organics are added to form a working solution. This method has the shortcoming that there is a considerable loss of the anthraquinone and the organic solvents from their hydrogenation, oxidation and thermal degradation plus the high cost of its processing, handling and storage.
The presence of these formed undesired organic byproducts with hydrogen, oxygen and hydrogen peroxide presents further safety hazards and further interactions between the solvents, feed gases and intermediates that can be formed. All such organic byproducts must be removed from the desired hydrogen peroxide product. These byproducts present waste treating problems.
Various methods have been attempted to directly combine oxygen and hydrogen. The direct combination of hydrogen and oxygen to form hydrogen peroxide has the advantage of an inherent simplification of chemistry and processing. The direct process, however, does require careful control of the gaseous mixture of hydrogen and oxygen, so that one is either always outside the flammable or explosive range of hydrogen and oxygen or operating conditions are selected where an explosive mixture can be safely handled.
Most direct hydrogen peroxide processes operate in an aqueous environment. These direct processes suffer two substantial economic handicaps. They operate with a continuous gaseous phase, which requires hydrogen to be below its lower flammable/explosive limit or 4–5%. This gives a low productivity-uneconomic reaction system. Secondly, such processes suffer a further economic handicap from the low solubility of hydrogen and oxygen in an aqueous (water) solution. The solubility of these gases can be several fold higher in organic solvents, leading to a smaller, less expensive reaction system. Under such conditions, there is no means to extinguish or quench the reaction with the equipment provided.
The processes for the direct production of hydrogen peroxide cannot operate within the flammable range of hydrogen with oxygen because of the presence of a continuous gas phase above the liquid level or the potential presence of large bubbles in the reaction system.
U.S. Pat. Nos. 5,641,467 and 6,042,804, describe producing hydrogen peroxide by injecting dispersed minute bubbles of hydrogen and oxygen into an acidic liquid containing solely water and a Group VIII metal catalyst. The regime of dispersed minute individual bubbles permits the quenching of any reaction that may occur within the bubble by the surrounding liquid thus permitting operating the reactor within the flammable range of hydrogen with oxygen plus diluents.
U.S. Pat. No. 5,965,101 describes the use of 90%–100% methanol reaction media in a conventional suspension or fixed bed reactor. Such a reactor gives a continuous gas phase, which limits the hydrogen content to under 5%. U.S. Pat. No. 5,399,334 uses a combination of halogen bearing organic and water in conventional reactor design.
U.S. Pat. Nos. 4,309,390; 4,336,240; 4,336,239; 4,336,238, all assigned to Air Products and Chemical, employ organic solvents with and without some water in agitated tank or other conventional reactors. U.S. Pat. Nos. 4,347,232 and 4,347,231 describe the use of water with halogenated organic solvent that has limited solubility for water and hydrogen peroxide. These patents teach the use of a conventional agitated tank reactor. U.S. Pat. No. 4,007,256 concerns the use of an organic-nitrogen compound with water in a fixed bed reactor.